Magnetic fluid seal device

ABSTRACT

A magnetic fluid seal device that increases a permissible value of eccentricity for two members to improve sealability and decreases a variation of quality by injecting a magnetic fluid before assembling of parts, that saves structural members to achieve thinning, and that is easy to produce. An annular magnet  3  is buoyantly supported by the magnetic fluid  4  and  5  retained, and the space between a housing  1  and a shaft  2  is sealed by the annular magnet  3  and magnetic fluid  4  and  5.

This is a nationalization of PCT/JP02/04938 filed May 22, 2002 andpublished in Japanese.

TECHNICAL FIELD

The present invention relates to a relatively moving magnetic fluid sealdevice, and is applied as a dust seal in production machines, such asdevices for manufacturing semiconductors, devices for manufacturingliquid crystal panel displays, devices for manufacturing hard disks, anddevices for manufacturing optical parts, and as a dust seal built intoproducts such as cameras, hard disk drives, and optical parts.

BACKGROUND ART

A conventional relatively moving magnetic fluid seal device seals a gapbetween two members by bringing a magnetic fluid that is retained at oneof the two members into contact with a surface of the other member.

An example configuration of a conventional magnetic fluid seal device isillustrated in FIG. 24. This is a configuration in which a magnet 103,which is commonly magnetized in an axial direction, is sandwichedbetween and adhered to two pole pieces 104, disposed in a nonmagnetichousing 101, and a magnetic fluid 105 is filled into gaps between thepole pieces 104 and a magnetic material shaft 102.

However, the following problems arise in the case of the above-describedconventional technology.

Because the magnetic fluid seal device of the conventional technology isfixed to the housing, the tolerance of eccentricity between the housingand the shaft becomes equal to or less than the gaps between the polepieces and the shaft, and high precision in the coaxiality between thehousing and the shaft has been necessary.

In this configuration, there has also been the complication that thefilling of the magnetic fluid must be conducted after assembly of thedevice, and there has been the drawback that it is difficult to managethe magnetic fluid filling amount.

Moreover, because a regular thickness is necessary for the magnet andthe pole pieces, there has been a limit to thinning. There has also beenthe drawback that the magnet and the pole pieces must be adhered.

The present invention was devised in order to solved the problems in theabove-described conventional technology, and it is an object thereof toprovide an easily manufacturable magnetic fluid seal device thatimproves sealability by enlarging the tolerance of eccentricity of thetwo members, that can reduce variations in quality by making it possibleto inject the magnetic fluid before device assembly, and that improvesthinning by reducing structural members.

DISCLOSURE OF THE INVENTION

The present invention adopts the following configurations in order tosolve the above-described problems.

In order to achieve the above-described object, the invention is amagnetic fluid seal device that seals a space between two members thatare assembled so as to be mutually relatively movable, the magneticfluid seal device including:

magnetic force generating means that is disposed between the two membersand generates a magnetic force; and

a magnetic fluid that is magnetically retained at opposing ends of themagnetic force generating means opposing the two members and that sealstwo gaps between the magnetic force generating means and each membersurface of the two members,

wherein the magnetic force generating means is buoyantly supported bythe magnetic fluid, and the space between the two members is sealed bythe magnetic force generating means and the magnetic fluid.

Thus, the sum of the two gaps between each member surface of the twomembers and the magnetic force generating means becomes a tolerance ofeccentricity of the two members, and sealability can be exhibited evenif the precision of coaxiality is low. Also, members such as the polepieces that have been conventionally used become unnecessary, structuralmembers can be reduced, which is effective for thinning of the device,and manufacturing becomes easy without the need to join like members.Moreover, because the magnetic force generating means floats with amagnetic force by the magnetic fluid, the invention also exhibits afunction as a rotation inertia damper using the magnetic forcegenerating means as an inertial body and using the magnetic fluid asviscous damping means.

It is preferable for the magnetic fluid seal device to further includesleeves that are fitted together with at least one member of the twomembers, and for a groove to be formed in opposing surfaces of thesleeves opposing the magnetic force generating means.

Thus, the device can be fitted in a state in which the magnetic fluid isfilled in advance between the magnetic force generating means and thesleeves, the fitting becomes easy, and management of the magnetic fluidfilling amount becomes easy.

It is preferable for the sleeves to include two cross-sectionallyL-shaped members comprising an axial-direction portion and a projectingportion that projects in a radial direction from the axial-directionportion at an opposite end portion at the axial direction, and for thesleeves to be configured by superposing the axial-direction portions ofthe cross-sectionally L-shaped members.

Thus, it becomes easy to dispose the magnetic force generating means inthe grooves of the sleeves. Also, because the magnetic fluid seal devicecan be configured without the structural parts having elasticdeformability, the degree of freedom with which materials can beselected becomes large.

It is preferable for an oil-repellant film to be formed on at least asurface portion, outside the groove, of the opposing surfaces of thesleeves opposing the magnetic force generating means.

Thus, it is possible to prevent the magnetic fluid from spreading on thesurfaces outside the grooves and to prevent the magnetic fluid amountused in the seal from being reduced.

It is preferable for a portion of the sleeves that projects in a radialdirection to be configured by a rubber-like elastic body.

Thus, it becomes easy to dispose the magnetic force generating meansinto the grooves of the sleeves by deforming the rubber-like elasticbody.

It is preferable for a portion of the sleeves that fits together withthe one of the members to be configured by a rubber-like elastic body.

Thus, adhesion of both in the fitting together of the sleeve with theone of the members becomes unnecessary.

It is preferable for the opposing ends of the magnetic force generatingmeans opposing the two members to be pointed, and for magnetic flux tobe concentrated at and for the magnetic fluid to be magneticallyretained at pointed tips thereof.

Thus, the magnetic fluid is efficiently concentrated and retainedwithout being dispersed, and it is thus possible to reduce the magneticfluid filling amount.

It is preferable for the grooves of the sleeves to be formed in a shapethat matches the pointed opposing ends of the magnetic force generatingmeans.

Thus, it is further possible to prevent dispersion of the magneticfluid.

It is preferable for the gaps between the pointed opposing ends of themagnetic force generating means and the grooves of the sleeves to narrowtowards the tips of the pointed opposing ends of the magnetic forcegenerating means.

Thus, it is further possible to reduce the magnetic fluid fillingamount.

It is preferable for the pointed opposing ends of the magnetic forcegenerating means to be cross-sectionally triangular protruding shapes.

Thus, the magnetic flux can be concentrated at, and the magnetic fluidcan be efficiently concentrated and retained at, the pointed tipsthereof.

It is preferable for the pointed opposing ends of the magnetic forcegenerating means to be cross-sectionally arced protruding shapes.

Thus, the magnetic flux can be concentrated at, and the magnetic fluidcan be efficiently concentrated and retained at, the pointed tipsthereof.

It is preferable for the magnetic fluid seal device to further includesleeves that are fitted together with at least one of the two members,and for an oil-repellant film to be formed on at least bothaxial-direction end portions of the sleeves.

Thus, the device can be fitted in a state in which the magnetic fluidhas been filled in advance between the magnetic force generating meansand the sleeves, the fitting becomes easy, and management of themagnetic fluid filling amount becomes easy. Also, it is possible toprevent the magnetic fluid from spreading onto both axial-direction endportions of the sleeves and to prevent the magnetic fluid filling amountfrom being reduced.

It is preferable for the two members to be relatively reciprocallymovable, and for the magnetic fluid seal device to include a sleeve thatfits together with at least one of the two members and extends in anaxial direction corresponding to a reciprocal movement length of the twomembers.

Thus, the device can be fitted in a state in which the magnetic fluidhas been filled in advance between the magnetic force generating meansand the sleeves, the fitting becomes easy, and management of themagnetic fluid filling amount becomes easy. Also, it is possible to makethe magnetic fluid slide on the sleeve extending in the axial directioncorresponding to the reciprocal movement length of the two members.

It is preferable for a groove corresponding to the reciprocal movementlength of the two members to be formed in an opposing surface of thesleeve opposing the magnetic force generating means.

Thus, the device can be fitted in a state in which the magnetic fluidhas been filled in advance between the magnetic force generating meansand the sleeves, the fitting becomes easy, and scattering of themagnetic fluid outside of the groove is prevented, so that management ofthe magnetic fluid filling amount becomes easy. Also, it is possible toprevent the magnetic fluid from sliding in the groove of the sleevecorresponding to the reciprocal movement length of the two members.

It is preferable for an oil-repellant film to be formed on the opposingsurface of the sleeve opposing the magnetic force generating means.

Thus, it is possible to prevent the magnetic fluid sliding at the timeof relative reciprocal movement from spreading on the surface and toprevent the magnetic fluid amount used in the seal from being reduced.

It is preferable for the sleeves to have an elastic deformationcharacteristic that enables the magnetic force generating means to beinserted into the grooves of the sleeves.

Thus, smooth fitting of the magnetic force generating means is possible.

It is preferable for the two members and the sleeves to be nonmagneticmaterials.

Thus, the magnetic fluid can be gathered at the magnetic poles of themagnetic force generating means and the magnetic force generating meanscan be made to float magnetically.

It is preferable for a groove to be formed in an opposing surface of atleast one member of the two members opposing the magnetic forcegenerating means.

Thus, members such as sleeves and pole pieces that have been usedconventionally become unnecessary, the device can be configured by onlythe magnetic force generating means and the magnetic fluid, structuralmembers can be reduced, and thinning becomes largely possible.

It is preferable for an oil-repellant film to be formed on an opposingsurface of at least one member of the two members opposing the magneticforce generating means.

Thus, it is possible to prevent the magnetic fluid from spreading on thesurface of the one member and to prevent the magnetic fluid amount usedin the seal from being reduced.

It is preferable for the magnetic force generating means to have anelastic deformation characteristic that enables the magnetic forcegenerating means to be inserted into the grooves.

Thus, smooth fitting of the magnetic force generating means is possible.

It is preferable for an oil-repellant film to be formed on a portion ofthe magnetic force generating means that does not contact the magneticfluid.

Thus, it is possible to prevent the magnetic fluid from spreading on thesurface of the magnetic force generating means and to prevent themagnetic fluid amount used in the seal from being reduced.

It is preferable for a cutout portion to be formed in a portion of themagnetic force generating means that does not contact the magneticfluid.

Thus, weight reduction of the magnetic force generating means isimproved, and it is possible to make the magnetic force generating meansfloat more reliably.

It is preferable for a cutout portion to be formed in a side surface ofthe magnetic force generating means extending between the two members.

Thus, weight reduction of the magnetic force generating means isimproved, and it is possible to make the magnetic force generating meansfloat more reliably.

It is preferable for cutout portions to be formed in center portions ofopposing end surfaces of the magnetic force generating means opposingthe two members.

Thus, weight reduction of the magnetic force generating means isimproved, and it is possible to make the magnetic force generating meansfloat more reliably.

It is preferable for the magnetic force generating means to be a magnetthat is unipolarly or multipolarly magnetized in the axial direction orthe radial direction.

Thus, the magnet and the magnetic fluid fill the space between the twomembers and can seal the two members.

A magnetic fluid seal device that seals a space between two members thatare assembled so as to be mutually relatively movable, characterized byincluding:

sleeve-like magnetic force generating means that are respectively fittedtogether with the two members and generate a magnetic force;

a nonmagnetic member that is disposed between the sleeve-like magneticforce generating means; and

magnetic fluid that is magnetically retained at opposing surfaces of thesleeve-like magnetic force generating means opposing the nonmagneticmember and that seals two gaps between the sleeve-like magnetic forcegenerating means and the nonmagnetic member,

wherein the nonmagnetic member is buoyantly supported by the magneticfluid, and the space between the two members is sealed by thenonmagnetic member and the magnetic fluid.

Thus, the sum of the two gaps between each member surface of the twomembers and the nonmagnetic member becomes a tolerance of eccentricityof the two members, and the magnetic fluid seal device can exhibitsealability even if the precision of the coaxiality is low. Also,members such as the pole pieces that have been conventionally usedbecome unnecessary, structural members can be reduced, which iseffective for thinning of the device, and manufacturing becomes easywithout the need to join members. Moreover, because the nonmagneticmember floats with a magnetic force by the magnetic fluid, the magneticfluid seal device also exhibits a function as a rotation inertia damperusing the nonmagnetic member as an inertial body and using the magneticfluid as viscous damping means. In particular, because nonmagneticmember can be made thin and light without changing the magnetic force,the nonmagnetic member can be made to float magnetically even if thediameter of the device is increased.

It is preferable for a groove to be formed in an opposing surface of atleast one of the sleeve-like magnetic force generating means opposingthe nonmagnetic member.

Thus, the device can be fitted in a state in which the magnetic fluidhas been filled in advance between the sleeve-like magnetic forcegenerating means and the nonmagnetic member, the fitting becomes easy,and management of the magnetic fluid filling amount becomes easy.

It is preferable for the sleeve-like magnetic force generating means toinclude two cross-sectionally L-shaped members comprising anaxial-direction portion and a projecting portion that projects in aradial direction from the axial-direction portion at an opposite endportion at the axial direction, and for the sleeve-like magnetic forcegenerating means to be configured by superposing the axial-directionportions of the cross-sectionally L-shaped members.

Thus, it becomes easy to dispose the nonmagnetic member in the groovesof the sleeve-like magnetic force generating means. Also, because themagnetic fluid seal device can be configured without structural partshaving elastic deformability, the degree of freedom with which materialscan be selected is increased.

It is preferable for an oil-repellant film to be formed on at least asurface portion, outside the groove, of the opposing surface of thesleeve-like magnetic force generating means opposing the nonmagneticmember.

Thus, it is possible to prevent the magnetic fluid from spreading on thesurface outside the groove and to prevent the magnetic fluid amount usedin the seal from being reduced.

It is preferable for an oil-repellant film to be formed on at least bothaxial-direction end portions of the sleeve-like magnetic forcegenerating means.

Thus, the device can be fitted in a state in which the magnetic fluidhad been filled in advance between the sleeve-like magnetic forcegenerating means and the nonmagnetic member, the fitting becomes easy,and management of the magnetic fluid filling amount becomes easy. Also,it is possible to prevent the magnetic fluid from spreading on bothaxial-direction end portions of the sleeve-like magnetic forcegenerating means and to prevent the magnetic fluid used in the seal frombeing reduced.

It is preferable for the two members to be relatively reciprocallymovable, and for the sleeve-like magnetic force generating means fittedtogether with at least one member of the two members to be extended inan axial direction corresponding to a reciprocal movement length of thetwo members.

Thus, the device can be fitted in a state in which the magnetic fluidhas been filled in advance between the sleeve-like magnetic forcegenerating means and the nonmagnetic member, the fitting becomes easy,and management of the filling amount becomes easy. Also, the magneticfluid can be retained on the sleeve-like magnetic force generating meansextending in the axial direction corresponding to the reciprocalmovement length of the two members.

It is preferable for a groove corresponding to the reciprocal movementlength of the two members to be formed in an opposing surface of thesleeve-like magnetic force generating means opposing the nonmagneticmember.

Thus, the device can be fitted in a state in which the magnetic fluidhas been filled in advance between the sleeve-like magnetic forcegenerating means and the nonmagnetic member, the fitting becomes easy,and scattering of the magnetic fluid outside of the groove is prevented,so that management of the magnetic fluid filling amount becomes easy.Also, the magnetic fluid can be retained in the groove of thesleeve-like magnetic force generating means corresponding to thereciprocal movement length of the two members.

It is preferable for the sleeve-like magnetic force generating means tohave an elastic deformation characteristic that enables the nonmagneticmember to be inserted into the grooves of the sleeve-like magnetic forcegenerating means.

Thus, smooth fitting of the nonmagnetic member is possible.

It is preferable for the nonmagnetic member to have an elasticdeformation characteristic that enables the nonmagnetic member to beinserted into the grooves of the sleeve-like magnetic force generatingmeans.

Thus, smooth fitting of the nonmagnetic member is possible.

It is preferable for an oil-repellant film to be formed on a portion ofthe nonmagnetic member that does not contact the magnetic fluid.

Thus, it is possible to prevent the magnetic fluid from spreading on thesurface of the nonmagnetic member and to prevent the magnetic fluidamount used in the seal from being reduced.

It is preferable for a cutout portion to be formed in a portion of thenonmagnetic member that does not contact the magnetic fluid.

Thus, weight reduction of the nonmagnetic member is improved and it ispossible to make the nonmagnetic member float more reliably.

It is preferable for a cutout portion to be formed in a side surface ofthe nonmagnetic member extending between the two members.

Thus, weight reduction of the nonmagnetic member is improved and it ispossible to make the nonmagnetic member float more reliably.

It is preferable for cutout portions to be formed in center portions ofopposing end surfaces of the nonmagnetic member opposing the twomembers.

Thus, weight reduction of the nonmagnetic member is improved and it ispossible to make the nonmagnetic member float more reliably.

It is preferable for the sleeve-like magnetic force generating means tobe a magnet that is unipolarly or multipolarly magnetized in the axialdirection or the radial direction.

Thus, the magnet is fitted to the two members and the magnetic fluid canbe retained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a half cross-sectional view illustrating a magnetic fluid sealdevice in accordance with a first embodiment.

FIG. 2 is a half cross-sectional view illustrating a magnetic fluid sealdevice in accordance with a second embodiment.

FIG. 3 is a half cross-sectional view illustrating a magnetic fluid sealdevice in accordance with a third embodiment.

FIG. 4 is a half cross-sectional view illustrating a magnetic fluid sealdevice in accordance with a fourth embodiment.

FIG. 5 is a half cross-sectional view illustrating a magnetic fluid sealdevice in accordance with a fifth embodiment.

FIG. 6 is a half cross-sectional view illustrating a magnetic fluid sealdevice in accordance with a sixth embodiment.

FIG. 7 is a half cross-sectional view illustrating a magnetic fluid sealdevice in accordance with a seventh embodiment.

FIG. 8 is a half cross-sectional view illustrating a magnetic fluid sealdevice in accordance with an eighth embodiment.

FIG. 9 is a half cross-sectional view illustrating a magnetic fluid sealdevice in accordance with a ninth embodiment.

FIG. 10 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a tenth embodiment.

FIGS. 11 are a half cross-sectional view illustrating a magnetic fluidseal device in accordance with an eleventh embodiment and viewsillustrating magnetized states of an annular magnet.

FIG. 12 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a twelfth embodiment.

FIG. 13 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a thirteenth embodiment.

FIG. 14 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a fourteenth embodiment.

FIG. 15 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a fifteenth embodiment.

FIG. 16 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a sixteenth embodiment.

FIG. 17 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a seventeenth embodiment.

FIG. 18 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with an eighteenth embodiment.

FIG. 19 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a nineteenth embodiment.

FIG. 20 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a twentieth embodiment.

FIG. 21 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a twenty-first embodiment.

FIG. 22 is a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a twenty-second embodiment.

FIGS. 23 are a half cross-sectional view illustrating a magnetic fluidseal device in accordance with a twenty-third embodiment and viewsillustrating magnetized states of a sleeve-like magnet.

FIG. 24 is a half cross-sectional view illustrating a magnetic fluidseal device of conventional technology.

BEST MODES FOR CARRYING OUT THE INVENTION

Preferable embodiments of the invention will be exemplarily described indetail below with reference to the drawings. However, unless otherwisespecified, dimensions, materials, forms, and relative disposition ofstructural parts disclosed in these embodiments are not intended tolimit the scope of the invention thereto. Also, unless new indication isgiven, materials, forms, and the like in regard to members that havealready been described once in the description below are the same asthose in their initial description.

The embodiments apply a magnetic fluid seal device as a dust seal inproduction machines, such as devices for manufacturing semiconductors,devices for manufacturing liquid crystal panel displays, devices formanufacturing hard disks, and devices for manufacturing optical parts,and as a dust seal built into products such as cameras, hard diskdrives, and optical parts.

FIRST EMBODIMENT

Using FIG. 1, the configuration of a magnetic fluid seal device inaccordance with a first embodiment will be described. FIG. 1 is a halfcross-sectional view illustrating the magnetic fluid seal device inaccordance with the first embodiment.

The magnetic fluid seal device illustrated in FIG. 1 is disposed betweena cylindrical housing 1 and a shaft 2 that is inserted into the housing1, which serve as two rotatably movable members. Relative rotationalmovement is conducted between the housing 1 and the shaft 2 and, in thepresent embodiment, only the shaft 2 rotates. The housing 1 and theshaft 2 are configured by nonmagnetic materials.

The magnetic fluid seal device includes an annular magnet 3 (magneticforce generating means), which is magnetized in the radial direction anddisposed between the housing 1 and the shaft 2, magnetic fluids 4 and 5,which are respectively retained at inner and outer peripheral endportions of the annular magnet 3, and sleeves 6 and 7, which arerespectively fitted together with the housing 1 and the shaft 2.

A magnetic field gradient is generated near inner and outer peripheralsurfaces, which are magnetic poles, of the annular magnet 3, themagnetic fluids 4 and 5 disposed inside these magnetic field gradientsare sucked in toward the upper field (magnet surface), and, as areaction force against it, the sleeves 6 and 7, which are nonmagneticmaterials, receive a repulsive force toward the lower magnetic field. Asa result, the annular magnet 3 floats in the magnetic fluids 4 and 5 ina state in which it does not contact the sleeves 6 and 7, and, at thesame time, the magnetic fluids 4 and 5 exhibit the function of sealingthe gaps between the annular magnet 3 and the sleeves 6 and 7.

It is preferable to use a plastic magnet that has a small specificgravity etc. as the annular magnet 3. The annular magnet 3 is preferablymagnetized in the longitudinal direction of the magnet cross-section (inthe present embodiment, the radial direction) in order to raise magneticfield strength near the magnet surface, and further improvement ispossible when the annular magnet 3 is multipolarly magnetized. However,the dimensions, material, and method of magnetization of the annularmagnet 3 are not limited to the above descriptions as long as theannular magnet 3 satisfies the condition that it floats in the magneticfluids 4 and 5 in a state in which it does not contact the sleeves 6 and7.

As the magnetic fluids 4 and 5, a fluid is used in which fine particlesof Fe₃O₄, Mn/ZnFe₂O₄, etc. are dispersed in colloid form in oil, water,an organic solvent, etc.

The sleeves 6 and 7 are cylindrical members made of a nonmagnetic metal,such as nonmagnetic stainless steel, an aluminum alloy, a copper alloy,or a titanium alloy, or a resin such as polyphenylene oxide,polycarbonate, or polyacetal, center portions are recessed and groovesare formed so that projecting portions project at both axial-directionend portions, and the inner and outer peripheral end portions of theannular magnet 3 have gaps that are respectively disposed in thegrooves. The magnetic fluids 4 and 5 are filled into the gaps betweeninner and outer peripheral ends of the annular magnet 3 and the groovesof the sleeves 6 and 7.

The sleeves 6 and 7 have an elastic deformation characteristic thatenables the annular magnet 3 to be inserted into the grooves of thesleeves 6 and 7, so that smooth fitting of the annular magnet 3 ispossible.

Oil-repellant films 8 and 9 are formed on surfaces of the projectingportions (i.e., the portions other than the inner grooves of thesurfaces opposing the annular magnet 3) of both axial-direction endportions of the sleeves 6 and 7. The magnetic fluids 4 and 5 within thegrooves of the sleeves 6 and 7 are prevented from spreading to theoutside by the oil-repellant films 8 and 9.

As processes for forming the oil-repellant films 8 and 9, there areprocesses by coating, application, and the like other than filmformation, and a material such as a fluorine oil-repellant agent isused.

The above magnetic fluid seal device is easily fitted with onetouch-between the housing 1 and the shaft 2 in a state in which themagnetic fluids 4 and 5 have been filled in advance between the annularmagnet 3 and the sleeves 6 and 7.

In the magnetic fluid seal device, the annular magnet 3 is buoyantlysupported by the retained magnetic fluids 4 and 5, and the annularmagnet 3 floats regardless of the orientation with which the device isdisposed.

The space between the housing 1 and the shaft 2 is sealed by the annularmagnet 3 and the magnetic fluids 4 and 5. As a result, the function thatseals the shaft 2 with respect to the housing 1 can be exhibited by theeccentricity of the sum of the two gaps between the inner and outerperipheral surfaces of the annular magnet 3 and the sleeves 6 and 7.

Therefore, because the magnetic fluid seal device has a configurationincluding gaps that retain the magnetic fluids 4 and 5 at both the innerand outer peripheries of the annular magnet 3, the sum of both gapsbecomes the tolerance of coaxiality of the housing 1 and the shaft 2,and sealability can be exhibited even when precision is low.

Because the annular magnet 3 floats with the magnetic force due to themagnetic fluids 4 and 5, the magnetic seal fluid device also exhibits afunction as a rotation inertia damper using the annular magnet 3 as aninertial body and using the magnetic fluids 4 and 5 as viscous dampingmeans.

Also, in regard to the members used in the magnetic fluid seal device,because there are no members such as pole pieces and only the annularmagnet 3 requires thickness, the structural members can be reduced andthe device can be thinned. Manufacture also becomes easy because thereis no need to join members with each other including members such as thepole pieces.

Moreover, because the inner and outer peripheral end portions of theannular magnet 3 are disposed in the grooves of the sleeves 6 and 7, thedevice can be fitted in a state in which the magnetic fluids 4 and 5have been filled in advance in the device, the fitting becomes easy, andmanagement of the magnetic fluid filling amount becomes easy.

SECOND EMBODIMENT

FIG. 2 illustrates a magnetic fluid seal device in accordance with asecond embodiment. The second embodiment is one in which anoil-repellant film 10 is formed on a radial-direction side surface ofthe annular magnet 3. Other configurations are the same as those of thefirst embodiment.

The oil-repellant film 10 is formed on the portion of the annular magnet3 that does not contact the magnetic fluids 4 and 5 (i.e., on theradial-direction side surface of the annular magnet 3 excluding cornerportions).

The oil-repellant film 10 is not formed on the corner portions of theradial-direction side surface of the annular magnet 3, and the cornerportions relate to the seal and magnetic buoyancy due to the adhesion ofthe magnetic fluids 4 and 5.

Thus, the spread of the magnetic fluids 4 and 5 on the radial-directionside surface of the annular magnet 3 and a reduction in the magneticfluid amount necessary for the seal can be prevented, and the sealingfunction can be exhibited with respect to any orientation with an evenless magnetic fluid filling amount that is filled in advance.

THIRD EMBODIMENT

FIG. 3 illustrates a magnetic fluid seal device in accordance with athird embodiment. The third embodiment is one in which a cutout portion11 is formed in the radial-direction side surface of the annular magnet3. Other configurations are the same as those of the first embodiment.

The cutout portion 11 is formed in the portion of the annular magnet 3that does not contact the magnetic fluids 4 and 5 (i.e., in theradial-direction side surface of the annular magnet 3 excluding cornerportions and extending between the housing 1 and the shaft 2).

Thus, weight reduction of the annular magnet 3 is improved, and theannular magnet 3 can float with respect to any orientation with an evenless magnetic fluid filling amount or with magnetic fluids 4 and 5 of aneven lower saturation magnetization.

FOURTH EMBODIMENT

FIG. 4 illustrates a magnetic fluid seal device in accordance with afourth embodiment. The fourth embodiment is one in which cutout portions12 are formed in center portions of the inner and outer peripheralsurfaces, in addition to the cutout portion 11 in the radial-directionside surface of the annular magnet 3. Other configurations are the sameas those of the first embodiment.

Similar to the third embodiment, the cutout portion 11 is formed in theportion of the annular magnet 3 that does not contact the magneticfluids 4 and 5 (i.e., in the radial-direction side surface of theannular magnet 3 excluding corner portions and extending between thehousing 1 and the shaft 2).

In addition, the cutout portions 12 are formed in the center portions ofthe inner and outer peripheral surfaces opposing the housing 1 or theshaft 2 excluding the corner portions of the annular magnet 3.

Thus, weight reduction of the annular magnet 3 is improved, and theannular magnet 3 can float with respect to any orientation with an evenless magnetic fluid filling amount or with magnetic fluids 4 and 5 of anlower saturation magnetization.

FIFTH EMBODIMENT

FIG. 5 illustrates a magnetic fluid seal device in accordance with afifth embodiment. The fifth embodiment is one in which no groove isformed in a sleeve 71 fitted together with the shaft 2 and in which theoil-repellant film 9 is formed on both axial-direction end portions ofopposing surfaces opposing the annular magnet 3. Other configurationsare the same as those of the first embodiment.

The sleeve 71 fitted together with the shaft 2 is a cylindrical shapethat does not have formed therein a groove such as the one in the firstembodiment. The oil-repellant film 9 is formed on both of theaxial-direction end portions of opposing surfaces opposing the annularmagnet 3.

In this configuration also, the annular magnet 3 floats with a magneticforce with respect to any orientation, and functions as a dust seal withrespect to the rotation of the shaft 2.

It should be noted that, as an alternative to the present embodiment,similar effects can be obtained by not forming the groove in the sleeveof the housing 1 and forming an oil-repellant film 8 on bothaxial-direction end portions of opposing surfaces opposing the annularmagnet 3.

SIXTH EMBODIMENT

FIG. 6 illustrates a magnetic fluid seal device in accordance with asixth embodiment. The sixth embodiment is one in which relativereciprocal movement is conducted between the housing 1 and the shaft 2,a sleeve 72 fitted together with the shaft 2 is extended in the axialdirection to a reciprocal movement length, and an oil-repellant film 13is formed on the entire opposing surface opposing the annular magnet 3.Other configurations are the same as those of the first embodiment.

In the present embodiment, not only is relative rotational movementconducted between the housing 1 and the shaft 2, but relative reciprocalmovement is also conducted between the housing 1 and the shaft 2, and,in the present embodiment, the shaft 2 reciprocally moves.

Thus, it is necessary to stabilize and support the magnetic fluid sealdevice by sliding the magnetic fluid, and, in the present embodiment,the device has a configuration in which the sleeve 72 fitted togetherwith the shaft 2 is extended in the axial direction to the length atwhich the shaft 2 reciprocally moves, and the magnetic fluid 5 on thesleeve 72 is slid.

In this instance, in order to prevent the magnetic fluid 5 fromspreading onto the sleeve 72, the oil-repellant film 13 is formed on theentire opposing surface opposing the annular magnet 3 on the sleeve 72fitted together with the shaft 2.

In this configuration also, the annular magnet 3 floats with a magneticforce with respect to any orientation, and functions as a dust seal withrespect to the rotational/reciprocal movement of the shaft 2. Thepresent embodiment is, of course, also suited for a case where the shaft2 only moves reciprocally.

It should be noted that, as an alternative to the present embodiment,similar effects can be obtained by extending the sleeve of the housing 1in the axial direction to the reciprocal movement length and forming theoil-repellant film on the entire opposing surface opposing the annularmagnet 3.

SEVENTH EMBODIMENT

FIG. 7 illustrates a magnetic fluid seal device in accordance with aseventh embodiment. The seventh embodiment is one in which relativereciprocal movement is conducted between the housing 1 and the shaft 2,a sleeve 73 fitted together with the shaft 2 is extended in the axialdirection to a reciprocal movement length without a groove being formedin the sleeve 73, and an oil-repellant film is formed on the entireopposing surface opposing the annular magnet 3. Other configurations arethe same as those of the first embodiment.

Similar to the sixth embodiment, in the present embodiment, not only isrelative rotational movement conducted between the housing 1 and theshaft 2, but relative reciprocal movement is also conducted between thehousing 1 and the shaft 2, and, in the present embodiment, the shaft 2reciprocally moves.

Thus, it is necessary to stabilize and support the magnetic fluid sealdevice by sliding the magnetic fluid, and, in the present embodiment,the device has a configuration in which the cylindrical sleeve 73 fittedtogether with the shaft 2 is extended in the axial direction to thelength at which the shaft 2 reciprocally moves, and the magnetic fluid 5on the sleeve 73 is slid.

In this instance, in order to prevent the magnetic fluid 5 fromspreading onto the sleeve 73, an oil-repellant film 14 is formed on theentire opposing surface opposing the annular magnet 3 on the sleeve 73fitted together with the shaft 2.

Here, contrary to the sixth embodiment, the sleeve 73 fitted togetherwith the shaft 2 is a cylindrical shape that does not have formedtherein a groove such as the one in the first embodiment.

In this configuration also, the annular magnet 3 floats with a magneticforce with respect to any orientation, and functions as a dust seal withrespect to the rotational/reciprocal movement of the shaft 2. Thepresent embodiment is, of course, also suited for a case where the shaft2 only moves reciprocally.

It should be noted that, as an alternative to the present embodiment,similar effects can be obtained by extending the sleeve of the housing 1in the axial direction to the reciprocal movement length and forming theoil-repellant film on the entire opposing surface opposing the annularmagnet 3, without there being formed a groove such as the one in thefirst embodiment.

EIGHTH EMBODIMENT

FIG. 8 illustrates a magnetic fluid seal device in accordance with aneighth embodiment. The eighth embodiment is one in which a groove isformed in the inner periphery of the housing 1, an annular magnet(rubber magnet, etc.) 31 having an elastic deformation characteristic isinserted therein, and the magnetic fluids 4 and 5 are filled into thegaps formed in the inner and outer peripheries of the annular magnet 31.Other configurations are the same as those of the first embodiment.

In the present embodiment, no sleeve is fitted together with the housing1 and the shaft 2, but a groove, which is disposed so that an outerperipheral end portion of the annular magnet 31 includes a gap, isdirectly formed in the housing 1.

Here, because it is necessary for the annular magnet 31 to be deformedand inserted into the groove of the housing 1, a rubber magnet having anelastic deformation characteristic (flexibility) is used.

After the annular magnet 31 has been inserted into the groove of thehousing 1, the magnetic fluid 4 is filled into the gap between thegroove of the housing 1 and the annular magnet 31, and the magneticfluid 5 is filled into the gap between the shaft 2 surface and theannular magnet 31.

In this configuration also, the annular magnet 31 floats with a magneticforce with respect to any orientation, and functions as a dust seal withrespect to the rotation of the shaft 2.

It should be noted that the same effects can be obtained with aconfiguration in which the groove is formed in the shaft 2 or aconfiguration in which grooves are formed in both of the housing 1 andthe shaft 2.

NINTH EMBODIMENT

FIG. 9 illustrates a magnetic fluid seal device in accordance with aninth embodiment. The ninth embodiment is one in which a gap is directlyformed between the shaft 2 surface and an annular magnet (rubber magnet,etc.) 32 having an elastic deformation characteristic, and in which agroove formed in a sleeve 61 of the housing 1 is formed deeply. Otherconfigurations are the same as those of the first embodiment.

In the present embodiment, no sleeve is fitted together with the shaft2, but a gap, into which the magnetic fluid 5 is filled, is directlyformed between the shaft 2 surface and the annular magnet (rubbermagnet, etc.) 32 having an elastic deformation characteristic(flexibility).

The sleeve 61 fitted together with the housing 1 includes the groovedeeply formed therein so that there is a large gap between the sleeve 61and the annular magnet 32 outer peripheral surface. The oil-repellantfilm 8 is formed on surfaces of projecting portions of bothaxial-direction end portions of the sleeve 61 (i.e., portions outsidethe groove inside the surface opposing the annular magnet 32).

In this configuration also, the function that seals the shaft 2 withrespect to the housing 1 can be exhibited even if there is eccentricityof the sum of the two gaps in the inner and outer peripheral surfaces ofthe annular magnet 32, and the annular magnet 32 floats with a magneticforce with respect to any orientation and functions as a dust seal withrespect to the rotational movement of the shaft 2.

TENTH EMBODIMENT

FIG. 10 illustrates a magnetic fluid seal device in accordance with atenth embodiment. The tenth embodiment is one in which, in the ninthembodiment, an oil-repellant film 15 is formed on the surface of theshaft 2 contacting the magnetic fluid 5. Other configurations are thesame as those of the first embodiment.

In the present embodiment, in addition to the configuration of the ninthembodiment, the oil-repellant film 15 is formed in advance on the shaft2 surface at least in a range that the magnetic fluid 5, which isretained at the annular magnet 32 inner peripheral surface, contactswhen the magnetic fluid seal device is fitted.

Thus, the magnetic fluid seal device can be fitted in a state in whichthe magnetic fluids 4 and 5 have been filled in advance in the magneticfluid seal device. Also, in the present embodiment, the magnetic fluidseal device functions as a dust seal with respect to reciprocal movementor rotational/reciprocal movement of the shaft 2.

ELEVENTH EMBODIMENT

FIG. 11 illustrate a magnetic fluid seal device in accordance with aneleventh embodiment. The eleventh embodiment is one in which, in thefirst embodiment, the sleeves 6 and 7 are each configured by two dividedcross-sectionally L-shaped members. Other configurations are the same asthose of the first embodiment.

As illustrated in FIG. 11( a), in this embodiment, the sleeves 6 and 7are each configured by two divided cross-sectionally L-shaped members.The two cross-sectionally L-shaped members comprise an axial-directionportion and a projecting portion that projects in the radial directionat the opposite end at the axial direction, and one sleeve 6 and 7 isformed by superposing the axial-direction portions of the twocross-sectionally L-shaped members.

Here, because the cross-sectionally L-shaped members at the right sideof the drawing are fitted first and then the cross-sectionally L-shapedmembers at the left side of the drawing are superposed thereon, thedevice can be easily configured by carrying out in advance thedisposition of the annular magnet 3 and the filling of the magneticfluids 4 and 5 at the cross-sectionally L-shaped members at the leftside of the drawing. Alternatively, the annular magnet 3 can be insertedwithin the cross-sectionally L-shaped members at the left side of thedrawing, the cross-sectionally L-shaped members at the right side of thedrawing can then be superposed thereon, and the magnetic fluids 4 and 5can be filled in, so that it can be fitted to the device in a state inwhich the device is assembled as a seal device.

Magnetized patterns of the annular magnet 3 in this case arerespectively illustrated in FIGS. 11( b) and 11(c). FIG. 11( b)illustrates a unipolarly magnetized annular magnet 3, and FIG. 11( c)illustrates a multipolarly magnetized annular magnet 3. These annularmagnets 3 include poles lined in the axial direction.

Thus, it becomes easy to dispose the annular magnet 3 into the groovesof the sleeves 6 and 7. Also, because the device can be configured evenif structural parts such as the annular magnet 3 and the sleeves 6 and 7do not have an elastic deformation characteristic, the degree of freedomwith which materials can be selected is increased.

TWELFTH EMBODIMENT

FIG. 12 illustrates a magnetic fluid seal device in accordance with atwelfth embodiment. The twelfth embodiment is one in which, in the firstembodiment, the sleeves 6 and 7 are each configured by a rigid portionand a rubber portion. Other configurations are the same as those of thefirst embodiment.

In the present embodiment, the sleeve 6 is configured by a rigid portion6 a and a rubber portion 6 b. The sleeve 7 is configured by a rigidportion 7 a and a rubber portion 7 b.

The rigid portions 6 a and 7 a are cross-sectionally L shapes thatinclude an axial-direction portion and a projecting portion thatprojects at the left side of the axial-direction portion in the drawing.

The rubber portions 6 b and 7 b are cross-sectionally L shapes thatinclude an axial-direction portion, which fits together with the housing1 or the shaft 2, and a projecting portion, which projects at the rightside of the axial-direction portion in the drawing. The rubber portions6 b and 7 b are rubber-like elastic bodies that are easily deformed.

The sleeves 6 and 7 can be easily configured by superposing theaxial-direction portions of the rubber portions 6 b and 7 b on theaxial-direction portions of the rigid portions 6 a and 7 a.

In this configuration, the sleeves 6 and 7 are configured in advance,the annular magnet 3 is inserted by bending the projecting portions ofthe rubber portions 6 b and 7 b of the configured sleeves 6 and 7, andthereafter the magnetic fluids 4 and 5 are filled in.

After the seal device has been completed by the insertion of the annularmagnet 3 into the sleeves 6 and 7 and the filling of the magnetic fluids4 and 5, the device is fitted by respectively fitting theaxial-direction portions of the rubber portions 6 b and 7 b of thesleeves 6 and 7 together with the housing 1 or the shaft 2.

Thus, the annular magnet 3 can be inserted by bending the projectingportions of the rubber portions 6 b and 7 b of the sleeves 6 and 7, sothat is becomes easy to dispose the annular magnet 3 into the grooves ofthe sleeves 6 and 7.

Also, the axial-direction portions of the rubber portions 6 b and 7 bcan be respectively fitted to the housing 1 or the shaft 2, so thatadhesion becomes unnecessary in the fitting together of both.

THIRTEENTH EMBODIMENT

FIG. 13 illustrates a magnetic fluid seal device in accordance with athirteenth embodiment. The thirteenth embodiment is one in which,similar to the twelfth embodiment, in the first embodiment, the sleeves6 and 7 are each configured by the rigid portion and the rubber portion.Other configurations are the same as those of the first embodiment.

In the present embodiment, the sleeve 6 is configured by the rigidportion 6 a and the rubber portion 6 b. The sleeve 7 is configured bythe rigid portion 7 a and the rubber portion 7 b.

The rigid portions 6 a and 7 a are cylindrical shapes comprisingaxial-direction portions that contact the magnetic fluids 4 and 5.

The rubber portions 6 b and 7 b include an axial-direction portion,which is fitted together with the housing 1 or the shaft 2, and aprojecting portion, which projects at the left and right sides of theaxial-direction portion in the drawing. The rubber portions 6 b and 7 bare rubber-like elastic bodies that are easily deformed.

The sleeves 6 and 7 can be easily configured by superposing the rigidportions 6 a and 7 a within the axial-direction portions of the rubberportions 6 b and 7 b.

In this configuration, the sleeves 6 and 7 are configured in advance,the annular magnet 3 is inserted by bending the projecting portions ofthe rubber portions 6 b and 7 b of the configured sleeves 6 and 7, andthereafter the magnetic fluids 4 and 5 are filled in.

After the seal device has been completed by the insertion of the annularmagnet 3 into the sleeves 6 and 7 and the filling of the magnetic fluids4 and 5, the device is fitted by respectively fitting theaxial-direction portions of the rubber portions 6 b and 7 b of thesleeves 6 and 7 together with the housing 1 or the shaft 2.

Thus, the annular magnet 3 can be inserted by bending the projectingportions of the rubber portions 6 b and 7 b of the sleeves 6 and 7, sothat is becomes easy to dispose the annular magnet 3 into the grooves ofthe sleeves 6 and 7.

Also, the axial-direction portions of the rubber portions 6 b and 7 bcan be respectively fitted to the housing 1 or the shaft 2, so thatadhesion becomes unnecessary in the fitting together of both.

FOURTEENTH EMBODIMENT

FIG. 14 illustrates a magnetic fluid seal device in accordance with afourteenth embodiment. The fourteenth embodiment is one in which,similar to the twelfth and thirteenth embodiments, in the firstembodiment, the sleeves 6 and 7 are each configured by the rigid portionand the rubber portion. Also, the shapes of the annular magnet 3 and thesleeves 6 and 7 have been deformed in order to reduce the filling amountof the magnetic fluids 3 and 4. Other configurations are the same asthose of the first embodiment.

In the present embodiment, ends of the annular magnet 3 opposing thehousing 1 and the shaft 2 are pointed in a protruding shape that iscross-sectionally triangular, and magnetic flux is concentrated at andthe magnetic fluids 4 and 5 are magnetically held at the pointed tips.

The sleeve 6 is configured by the rigid portion 6 a and the rubberportion 6 b. The sleeve 7 is configured by the rigid portion 7 a and therubber portion 7 b.

The grooves of the sleeves 6 and 7 are cross-sectionally triangulargrooves that match the cross-sectionally triangular ends of the annularmagnet 3 that are pointed in a protruding manner and face the housing 1and the shaft 2.

The rigid portions 6 a and 7 a form tapers at one side and configuregroove wall surfaces of the sleeves 6 and 7 at the left side of thedrawing.

The rubber portions 6 b and 7 b include an axial-direction portion,which fits together with the housing 1 or the shaft 2, and a projectingportion, which projects and forms a groove wall surface of the sleeves 6and 7 at the right side of the axial-direction portion in the drawing.The rubber portions 6 b and 7 b are rubber-like elastic bodies that areeasily deformed.

The sleeves 6 and 7 can be easily configured by superposing the rigidportions 6 a and 7 a within the axial-direction portions of the rubberportions 6 b and 7 b.

In this configuration, the sleeves 6 and 7 are configured in advance,the annular magnet 3 is inserted by bending the projecting portions ofthe rubber portions 6 b and 7 b of the configured sleeves 6 and 7, andthereafter the magnetic fluids 4 and 5 are filled in.

After the seal device has been completed by the insertion of the annularmagnet 3 into the sleeves 6 and 7 and the filling of the magnetic fluids4 and 5, the device is fitted by respectively fitting theaxial-direction portions of the rubber portions 6 b and 7 b of thesleeves 6 and 7 together with the housing 1 or the shaft 2.

Thus, the annular magnet 3 can be inserted by bending the projectingportions of the rubber portions 6 b and 7 b of the sleeves 6 and 7, sothat is becomes easy to dispose the annular magnet 3 into the grooves ofthe sleeves 6 and 7.

Also, because the magnetic flux is concentrated at and the magneticfluids 4 and 5 are magnetically retained at the pointed tips of theannular magnet 3 that oppose the housing 1 and the shaft 2 and arepointed in a protruding shape that is triangular in cross section, themagnetic fluids 4 and 5 are efficiently concentrated and retainedwithout being dispersed. Thus, the magnetic fluid filling amount can bereduced.

Moreover, the axial-direction portions of the rubber portions 6 b and 7b can be respectively fitted together with the housing 1 or the shaft 2,so that adhesion becomes unnecessary in the fitting together of both.

FIFTEENTH EMBODIMENT

FIG. 15 illustrates a magnetic fluid seal device in accordance with afifteenth embodiment. The fifteenth embodiment is one in which, similarto the twelfth, thirteenth, and fourteenth embodiments, in the firstembodiment, the sleeves 6 and 7 are each configured by the rigid portionand the rubber portion. Also, similar to the fourteenth embodiment, theshapes of the annular magnet 3 and the sleeves 6 and 7 have beendeformed in order to reduce the filling amount of the magnetic fluids 3and 4. Other configurations are the same as those of the firstembodiment.

In the present embodiment, ends of the annular magnet 3 opposing thehousing 1 and the shaft 2 are pointed in a protruding shape that iscross-sectionally arced, and magnetic flux is concentrated at and themagnetic fluids 4 and 5 are magnetically held at the pointed tips.

The sleeve 6 is configured by the rigid portion 6 a and the rubberportion 6 b. The sleeve 7 is configured by the rigid portion 7 a and therubber portion 7 b.

The grooves of the sleeves 6 and 7 are cross-sectionally arced groovesthat match the cross-sectionally arced ends of the annular magnet 3 thatare pointed in a protruding manner and oppose the housing 1 and theshaft 2.

The gaps between the grooves of the sleeves 6 and 7 and thecross-sectionally arced ends of the annular magnet 3 that are pointed ina protruding manner narrow toward tips of the cross-sectionally arcedends of the annular magnet 3 that are pointed in a protruding manner.

The rigid portions 6 a and 7 a form cross-sectionally arced tapers atone side and configure groove wall surfaces of the sleeves 6 and 7 atthe left side of the drawing.

The rubber portions 6 b and 7 b include an axial-direction portion,which fits together with the housing 1 or the shaft 2, and a projectingportion, which projects and configures a groove wall surface of thesleeves 6 and 7 at the right side of the axial-direction portion in thedrawing. The rubber portions 6 b and 7 b are rubber-like elastic bodiesthat are easily deformed.

The sleeves 6 and 7 can be easily configured by superposing the rigidportions 6 a and 7 a within the axial-direction portions of the rubberportions 6 b and 7 b.

In this configuration, the sleeves 6 and 7 are configured in advance,the annular magnet 3 is inserted by bending the projecting portions ofthe rubber portions 6 b and 7 b of the configured sleeves 6 and 7, andthereafter the magnetic fluids 4 and 5 are filled in.

After the seal device has been completed by the insertion of the annularmagnet 3 into the sleeves 6 and 7 and the filling of the magnetic fluids4 and 5, the device is fitted by respectively fitting theaxial-direction portions of the rubber portions 6 b and 7 b of thesleeves 6 and 7 together with the housing 1 or the shaft 2.

Thus, the annular magnet 3 can be inserted by bending the projectingportions of the rubber portions 6 b and 7 b of the sleeves 6 and 7, sothat is becomes easy to dispose the annular magnet 3 into the grooves ofthe sleeves 6 and 7.

Also, because the magnetic flux is concentrated at and the magneticfluids 4 and 5 are magnetically held at the pointed tips of the annularmagnet 3 that oppose housing 1 and the shaft 2 and are pointed in aprotruding shape that is cross-sectionally arced, the magnetic fluids 4and 5 are efficiently concentrated and retained without being dispersed.Thus, the magnetic fluid filling amount can be reduced.

Because the gaps between the grooves of the sleeves 6 and 7 and thecross-sectionally arced ends of the annular magnet 3 that are pointed ina protruding manner narrow toward tips of the cross-sectionally arcedends of the annular magnet 3 that are pointed in a protruding manner, itbecomes easy for the magnetic fluids 4 and 5 to be concentrated at thenarrowest portion of the gaps, and the magnetic fluid filling amount canbe further reduced.

Moreover, the axial-direction portions of the rubber portions 6 b and 7b can be respectively fitted together with the housing 1 or the shaft 2,so that adhesion becomes unnecessary in the fitting together of both.

SIXTEENTH EMBODIMENT

The configuration of a magnetic fluid seal device in accordance with asixteenth embodiment will be described using FIG. 16. FIG. 16 is a halfcross-sectional view illustrating the magnetic fluid seal device inaccordance with the sixteenth embodiment.

The embodiment below is one in which a nonmagnetic member ismagnetically floated in consideration of the fact that, in the first tofifteenth embodiments, there is a limit on increasing diameter in thatthe force of buoyancy of the annular magnet becomes smaller than theforce of gravity of the annular magnet when the axial diameter becomeslarge.

The magnetic fluid seal device illustrated in FIG. 16 is disposedbetween the cylindrical housing 1 and the shaft 2 inserted into thehousing 1, which serve as two rotatably movable members. Relativerotational movement is conducted between the housing 1 and the shaft 2,and, in the present embodiment, only the shaft 2 rotates. The housing 1and the shaft 2 are configured by nonmagnetic materials.

The magnetic fluid seal device includes sleeve-like magnets 15 and 16(sleeve-like magnetic force generating means), which are respectivelyfitted together with the housing 1 and the shaft 2, a nonmagnetic member17, which is disposed between the housing 1 and the shaft 2, and themagnetic fluids 4 and 5, which are respectively retained at the innerand outer peripheries of the sleeve-like magnets 15 and 16.

A magnetic field gradient is generated near an inner peripheral surfaceof the sleeve-like magnet 15 and the outer peripheral surface of thesleeve-like magnet 16, the magnetic fluids 4 and 5 disposed inside thatmagnetic field gradient are sucked in toward the upper magnetic field(magnet surfaces), and, as a reaction force against it, the nonmagneticmember 17 receives a repulsive force toward the lower magnetic field. Asa result, the nonmagnetic member 17 floats in the magnetic fluids 4 and5 in a state in which it does not contact the sleeve-like magnets 15 and16, and, at the same time, the magnetic fluids 4 and 5 fulfill thefunction of sealing the gaps between the nonmagnetic member 17 and thesleeve-like magnets 15 and 16.

It is preferable to use, as the material for the sleeve-like magnets 15and 16, a rubber magnet or the like that has flexibility. Any method(direction, pole number) may be used for the magnetization of thesleeve-like magnets 15 and 16 as long as it satisfies the condition thatthe nonmagnetic member 17 floats in the magnetic fluids 4 and 5 in astate in which it does not contact the sleeve-like magnets 15 and 16.

As the magnetic fluids 4 and 5, a fluid is used in which fine particlesof Fe₃O₄, Mn.ZnFe₂O₄, etc. are dispersed in colloid form in oil, water,an organic solvent, etc.

As the material of the nonmagnetic member 17, a nonmagnetic metal, suchas nonmagnetic stainless steel, an aluminum alloy, a copper alloy, or atitanium alloy, or a resin, such as polyphenylene oxide, polycarbonate,or polyacetal, is preferable.

Center portions of the sleeve-like magnets 15 and 16 are recessed toform grooves, so that projecting portions project at bothaxial-direction end portions, and inner and outer peripheral endportions of the nonmagnetic member 17 have gaps that are respectivelydisposed in the grooves. The magnetic fluids 4 and 5 are filled into thegaps between inner and outer peripheral ends of the nonmagnetic member17 and the grooves of the sleeve-like magnets 15 and 16.

The sleeve-like magnets 15 and 16 have an elastic deformationcharacteristic that enables the nonmagnetic member 17 to be insertedinto the grooves of the sleeve-like magnets 15 and 16, so that smoothfitting of the nonmagnetic member 17 is possible.

When a sintered metallic material that does not have flexibility but hasa strong magnetic force is used for the sleeve-like magnets 15 and 16,it is preferable to use a material that has flexibility, such as resinor rubber, for the nonmagnetic member 17.

Oil-repellant films 18 and 19 are formed on surfaces of the projectingportions (i.e., the portions other than the inner grooves of the surfaceopposing the nonmagnetic member 17) of both axial-direction end portionsof the sleeve-like magnets 15 and 16. The magnetic fluids 4 and 5 withinthe grooves of the sleeve-like magnets 15 and 16 are prevented fromspreading to the outside by the oil-repellant films 18 and 19.

As processes for forming the oil-repellant films 18 and 19, there areprocesses by coating, application, and the like other than filmformation, and a material such as a fluorine oil-repellant agent isused.

The above magnetic fluid seal device is easily fitted with one touchbetween the housing 1 and the shaft 2 in a state in which the magneticfluids 4 and 5 have been pre-filled between the nonmagnetic member 17and the sleeve-like magnets 15 and 16.

In the magnetic fluid seal device, the nonmagnetic member 17 isbuoyantly supported by the magnetic fluids 4 and 5 retained by thesleeve-like magnets 15 and 16, and the nonmagnetic member 17 floatsregardless of the orientation with which the device is disposed.

The space between the housing 1 and the shaft 2 is sealed by thenonmagnetic member 17 and the magnetic fluids 4 and 5. As a result, thefunction that seals the shaft 2 with respect to the housing 1 can beexhibited by the eccentricity of the sum of the two gaps between theinner and outer peripheral surfaces of the nonmagnetic member 17 and thesleeve-like magnets 15 and 16.

Therefore, because the magnetic fluid seal device has a configurationincluding gaps that retain the magnetic fluids 4 and 5 at both the innerand outer peripheries of the nonmagnetic member 17, the sum of both gapsbecomes the tolerance of coaxiality of the housing 1 and the shaft 2,and sealability can be exhibited even when precision is low.

Because the nonmagnetic member 17 floats with the magnetic force due tothe magnetic fluids 4 and 5 that the sleeve-like magnets 15 and 16retain, the magnetic seal fluid device also exhibits a function as arotation inertia damper using the nonmagnetic member 17 as an inertialbody and using the magnetic fluids 4 and 5 as viscous damping means.

Also, in regard to the members used in the magnetic fluid seal device,because there are no members such as pole pieces and only thenonmagnetic member 17 requires thickness, the structural members can bereduced and the device can be thinned. Manufacture also becomes easybecause there is no need to join members with each other includingmembers such as the pole pieces.

Moreover, because the inner and outer peripheral end portions of thenonmagnetic member 17 are disposed in the grooves of the sleeve-likemagnets 15 and 16, the device can be fitted in a state in which themagnetic fluids 4 and 5 have been filled in advance in the device, thefitting becomes easy, and management of the magnetic fluid fillingamount becomes easy.

In contrast to the first to fifteenth embodiments, in which an annularmagnet is magnetically floated, the nonmagnetic member 17 can be madethin and light without changing the magnetic force because thenonmagnetic member is magnetically floated. Thus, the nonmagnetic member17 can be magnetically floated even if the diameter of the device ismade larger in a case where the axial diameter becomes large.

It should be noted that the magnetized direction of the sleeve-likemagnets in the present embodiment and in the embodiments below may beeither the radial direction or the axial direction.

SEVENTEENTH EMBODIMENT

FIG. 17 illustrates a magnetic fluid seal device in accordance with aseventeenth embodiment. The seventeenth embodiment is one in which anoil-repellant film 20 is formed on a radial-direction side surface ofthe nonmagnetic member 17. Other configurations are the same as those ofthe sixteenth embodiment.

The oil-repellant film 20 is formed on the portion of the nonmagneticmember 17 that does not contact the magnetic fluids 4 and 5 (i.e., onthe radial-direction side surface of the nonmagnetic member 17 excludingcorner portions).

The oil-repellant film 20 is not formed on the corner portions of theradial-direction side surface of the nonmagnetic member 17, and thecorner portions relate to the seal and magnetic buoyancy due to theadhesion of the magnetic fluids 4 and 5.

Thus, the magnetic fluids 4 and 5 do not spread on the radial-directionside surface of the nonmagnetic member 17, a reduction in the magneticfluid amount necessary for the seal can be prevented, and the sealingfunction can be exhibited with respect to any orientation with an evenless magnetic fluid filling amount that is filled in advance.

EIGHTEENTH EMBODIMENT

FIG. 18 illustrates a magnetic fluid seal device in accordance with aneighteenth embodiment. The eighteenth embodiment is one in which acutout portion 21 is formed in the radial-direction side surface of thenonmagnetic member 17. Other configurations are the same as those of thesixteenth embodiment.

The cutout portion 21 is formed in the portion of the nonmagnetic member17 that does not contact the magnetic fluids 4 and 5 (i.e., in theradial-direction side surface of the nonmagnetic member 17 excludingcorner portions and extending between the housing 1 and the shaft 2).

Thus, weight reduction of the nonmagnetic member 17 is improved, and thenonmagnetic member 17 can float with respect to any orientation with aneven less magnetic fluid filling amount or with magnetic fluids 4 and 5of an even lower saturation magnetization.

NINETEENTH EMBODIMENT

FIG. 19 illustrates a magnetic fluid seal device in accordance with anineteenth embodiment. The nineteenth embodiment is one in which cutoutportions 22 are formed in center portions of the inner and outerperipheral surfaces, in addition to the cutout portion 21 in theradial-direction side surface of the nonmagnetic member 17. Otherconfigurations are the same as those of the sixteenth embodiment.

Similar to the third embodiment, the cutout portion 21 is formed in theportion of the nonmagnetic member 17 that does not contact the magneticfluids 4 and 5 (i.e., in the radial-direction side surface of thenonmagnetic member 17 excluding corner portions and extending betweenthe housing 1 and the shaft 2).

In addition, the cutout portions 22 are formed in the center portions ofthe inner and outer peripheral surfaces opposing the housing 1 or theshaft 2 excluding the corner portions of the nonmagnetic member 17.

Thus, weight reduction of the nonmagnetic member 17 is improved, and thenonmagnetic member 17 can float with respect to any orientation with aneven less magnetic fluid filling amount or with magnetic fluids 4 and 5of an even lower saturation magnetization.

TWENTIETH EMBODIMENT

FIG. 20 illustrates a magnetic fluid seal device in accordance with atwentieth embodiment. The twentieth embodiment is one in which no grooveis formed in a sleeve-like magnet 161 fitted together with the shaft 2and in which the oil-repellant film 19 is formed at both axial-directionend portions of opposing surfaces opposing the nonmagnetic member 17.Other configurations are the same as those of the sixteenth embodiment.

The sleeve-like magnet 161 fitted together with the shaft 2 is acylindrical shape that does not have formed therein a groove such as theone in the eleventh embodiment. The oil-repellant film 19 is formed atthe axial-direction end portions of opposing surfaces opposing thenonmagnetic member 17.

In this configuration also, the magnetic fluid 5 is retained on thesleeve-like magnet 161, the nonmagnetic member 17 floats with a magneticforce with respect to any orientation and functions as a dust seal withrespect to the rotation of the shaft 2.

It should be noted that, as an alternative to the present embodiment,similar effects can be obtained by not forming the groove in thesleeve-like magnet of the housing 1 and forming the oil-repellant film18 at both axial-direction end portions of opposing surfaces opposingthe nonmagnetic member 17.

TWENTY-FIRST EMBODIMENT

FIG. 21 illustrates a magnetic fluid seal device in accordance with atwenty-first embodiment. The twenty-first embodiment is one in whichrelative reciprocal movement is conducted between the housing 1 and theshaft 2, and a sleeve-like magnet 162 fitted together with the shaft 2is extended in the axial direction to a reciprocal movement length.Other configurations are the same as those of the sixteenth embodiment.

In the present embodiment, not only is relative rotational movementconducted between the housing 1 and the shaft 2, but relative reciprocalmovement is also conducted between the housing 1 and the shaft 2, and,in the present embodiment, the shaft 2 reciprocally moves.

Thus, it is necessary to float the nonmagnetic member 17 by retainingthe magnetic fluid 5 at the entire planar portion on the sleeve-likemagnet 162, stabilize and support the magnetic fluid seal device, and,in the present embodiment, the device has a configuration in which thesleeve-like magnet 162 fitted together with the shaft 2 is extended inthe axial direction to the length at which the shaft 2 reciprocallymoves, and the magnetic fluid 5 on the sleeve-like magnet 162 isretained at the entire planar portion.

In this instance, in order to prevent the magnetic fluid 5 fromspreading onto the sleeve-like magnet 162, the oil-repellant film 19 isformed at both axial-direction end portions of the sleeve-like magnet162 fitted together with the shaft 2.

In this configuration also, the nonmagnetic member 17 floats with amagnetic force with respect to any orientation, and functions as a dustseal with respect to the rotational/reciprocal movement of the shaft 2.The present embodiment is, of course, also suited for a case where theshaft 2 only carries out reciprocal movement.

It should be noted that, as an alternative to the present embodiment,similar effects can be obtained by extending the sleeve-like magnet ofthe housing 1 in the axial direction to the reciprocal movement lengthand retaining the magnetic fluid at the opposing surface opposing thenonmagnetic member 17.

TWENTY-SECOND EMBODIMENT

FIG. 22 illustrates a magnetic fluid seal device in accordance with atwenty-second embodiment. The twenty-second embodiment is one in whichrelative reciprocal movement is conducted between the housing 1 and theshaft 2, a sleeve-like magnet 163 fitted together with the shaft 2 isextended in the axial direction to a reciprocal movement length withoutforming a groove in the sleeve-like magnet 163, the magnetic fluid 5 isretained at the planar portion excluding both axial-direction endportions of the opposing surface opposing the nonmagnetic member 17, andthe oil-repellant film 19 is formed on both axial-direction endportions. Other configurations are the same as those of the sixteenthembodiment.

Similar to the twentieth embodiment, in the present embodiment, not onlyis relative rotational movement conducted between the housing 1 and theshaft 2, but relative reciprocal movement is also conducted between thehousing 1 and the shaft 2, and, in the present embodiment, the shaft 2reciprocally moves.

Thus, it is necessary to float the nonmagnetic member 17 by retainingthe magnetic fluid 5 at the planar portion on the sleeve-like magnet 163excluding both axial-direction end portions, stabilize and support themagnetic fluid seal device, and, in the present embodiment, the devicehas a configuration in which the sleeve-like magnet 163 fitted togetherwith the shaft 2 is extended in the axial direction to the length atwhich the shaft 2 reciprocally moves, and the magnetic fluid 5 on thesleeve-like magnet 163 is retained at the planar portion excluding bothaxial-direction end portions.

In this instance, in order to prevent the magnetic fluid 5 fromspreading onto the sleeve-like magnet 163, the oil-repellant film 19 isformed at both axial-direction end portions of the opposing surfaceopposing the nonmagnetic member 17 on the sleeve-like magnet 163 fittedtogether with the shaft 2.

Here, contrary to the twenty-first embodiment, the sleeve-like magnet163 fitted together with the shaft 2 is a cylindrical shape that doesnot have formed therein a groove such as the one in the sixteenthembodiment.

In this configuration also, the nonmagnetic member 17 floats with amagnetic force with respect to any orientation, and functions as a dustseal with respect to the rotational/reciprocal movement of the shaft 2.The present embodiment is, of course, also suited for a case where theshaft 2 only carries out reciprocal movement.

It should be noted that, as an alternative to the present embodiment,similar effects can be obtained by extending the sleeve-like magnet ofthe housing 1 in the axial direction to the reciprocal movement length,and retaining the magnetic fluid at the opposing surface opposing thenonmagnetic member 17, without a groove such as the one in the sixteenthembodiment being formed.

TWENTY-THIRD EMBODIMENT

FIGS. 23 illustrate a magnetic fluid seal device in accordance with atwenty-third embodiment. The twenty-third embodiment is one in which, inthe sixteenth embodiment, the sleeve-like magnets 15 and 16 are eachconfigured by two divided cross-sectionally L-shaped members. Otherconfigurations are the same as those of the sixteenth embodiment.

As illustrated in FIG. 23( a), in this embodiment, the sleeve-likemagnets 15 and 16 are each configured by two cross-sectionally L-shapedmembers that have been divided into two. The two cross-sectionallyL-shaped members comprise an axial-direction portion and a projectingportion that projects in the radial direction at the opposite end at theaxial direction, and one sleeve-like magnet 15 and 16 is formed bysuperposing the axial-direction portions of the two cross-sectionallyL-shaped members.

Here, because the cross-sectionally L-shaped members at the right sideof the drawing are fitted first and then the cross-sectionally L-shapedmembers at the left side of the drawing are superposed thereon, thedevice can be easily configured by carrying out in advance thedisposition of the nonmagnetic member 17 and the filling of the magneticfluids 4 and 5 at the cross-sectionally L-shaped members at the leftside of the drawing. Alternatively, the nonmagnetic member 17 can beinserted within the cross-sectionally L-shaped members at the left sideof the drawing, the cross-sectionally L-shaped members at the right sideof the drawing can then be superposed thereon, and the magnetic fluids 4and 5 can be filled in, so that it can be fitted to the device in astate in which the device is assembled as a seal device.

Magnetized patterns of the sleeve-like magnet 15 in this case arerespectively illustrated in FIGS. 23( b) and 23(c). FIG. 23( b)illustrates a unipolarly magnetized sleeve-like magnet 15, and FIG. 23(c) illustrates a multipolarly magnetized sleeve-like magnet 15. Thesesleeve-like magnets 15 include poles lined in the axial direction.

Thus, it becomes easy to dispose the nonmagnetic member 17 into thegrooves of the sleeve-like magnets 15 and 16. Also, because the devicecan be configured even if structural parts such as the nonmagneticmember 17 and the sleeve-like magnets 15 and 16 do not have an elasticdeformation characteristic, the degree of freedom with which materialscan be selected is increased.

INDUSTRIAL APPLICABILITY

As described above, in the present invention, the magnetic forcegenerating means is buoyantly supported by the magnetic fluid, and thespace between the two members is sealed by the magnetic force generatingmeans and the magnetic fluid, whereby the sum of the two gaps betweeneach member surface of the two members and the magnetic force generatingmeans becomes a tolerance of eccentricity of the two members andsealability can be exhibited even if the precision of coaxiality is low.Also, members such as the pole pieces that have been conventionally usedbecome unnecessary, structural members can be reduced, which iseffective for thinning of the device, and manufacturing becomes easywithout the need to join members. Moreover, because the magnetic forcegenerating means floats with a magnetic force by the magnetic fluid, theinvention also exhibits a function as a rotation inertia damper usingthe magnetic force generating means as an inertial body and using themagnetic fluid as viscous damping means.

By disposing the sleeves that are fitted together with at least one ofthe two members and forming grooves in the opposing surface of thesleeve opposing the magnetic force generating means, the device can befitted in a state in which the magnetic fluid is filled in advancebetween the magnetic force generating means and the sleeves, the fittingbecomes easy, and management of the magnetic fluid filling amountbecomes easy.

The sleeves include two cross-sectionally L-shaped members comprisingthe axial-direction portion and the projecting portion that projects inthe radial direction from the axial-direction portion at the oppositeend portion at the axial direction, and are configured by superposingthe axial-direction portions of the cross-sectionally L-shaped members,whereby it becomes easy to dispose the magnetic force generating meansin the grooves of the sleeves. Also, because the invention can beconfigured without the structural parts having elastic deformability,the degree of freedom with which materials can be selected is increased.

The oil-repellant film is formed on at least the surface portion,outside the grooves, of the opposing surfaces of the sleeves opposingthe magnetic force generating means, whereby it is possible to preventthe magnetic fluid from spreading on the surfaces outside the groovesand to prevent the magnetic fluid amount used in the seal from beingreduced.

The portion of the sleeves that projects in the radial direction isconfigured by a rubber-like elastic body, whereby it becomes easy todispose the magnetic force generating means in the grooves of thesleeves by deforming the rubber-like elastic body.

The portion of the sleeves that fits together with the one of themembers is configured by a rubber-like elastic body, whereby adhesion ofboth in the fitting together of the sleeve with the one of the membersbecomes unnecessary.

The opposing ends of the magnetic force generating means opposing thetwo members are pointed, and magnetic flux is concentrated at and themagnetic fluid is magnetically retained at pointed tips thereof, wherebythe magnetic fluid is efficiently concentrated and retained withoutbeing dispersed, and it is thus possible to reduce the magnetic fluidfilling amount.

The grooves of the sleeves are formed in a shape that matches thepointed opposing ends of the magnetic force generating means, whereby itis further possible to prevent dispersion of the magnetic fluid.

The gaps between the pointed opposing ends of the magnetic forcegenerating means and the grooves of the sleeves narrow towards the tipsof the pointed opposing ends of the magnetic force generating means,whereby it is further possible to reduce the magnetic fluid fillingamount.

The pointed opposing ends of the magnetic force generating means arecross-sectionally triangular protruding shapes, whereby the magneticflux can be concentrated at, and the magnetic fluid can be efficientlyconcentrated and retained at, the pointed tips thereof.

The pointed opposing ends of the magnetic force generating means arecross-sectionally arced protruding shapes, whereby the magnetic flux canbe concentrated at, and the magnetic fluid can be efficientlyconcentrated and retained at, the pointed tips thereof.

The device includes sleeves that are fitted together with at least oneof the two members, and the oil-repellant film is formed on at leastboth axial-direction end portions of the sleeves, whereby the device canbe fitted in a state in which the magnetic fluid has been filled inadvance between the magnetic force generating means and the sleeves, thefitting becomes easy, and management of the magnetic fluid fillingamount becomes easy. Also, it is possible to prevent the magnetic fluidfrom spreading onto both axial-direction end portions of the sleeves andto prevent the magnetic fluid amount used in the seal from beingreduced.

The two members are relatively reciprocally movable, and the deviceincludes the sleeve that fits together with at least one of the twomembers and extends in the axial direction corresponding to thereciprocal movement length of the two members, whereby the device can befitted in a state in which the magnetic fluid has been filled in advancebetween the magnetic force generating means and the sleeves, the fittingbecomes easy, and management of the magnetic fluid filling amountbecomes easy. Also, it is possible to make the magnetic fluid slide onthe sleeve extending in the axial direction corresponding to thereciprocal movement length of the two members.

The groove corresponding to the reciprocal movement length of the twomembers is formed in the opposing surface of the sleeve opposing themagnetic force generating means, whereby the device can be fitted in astate in which the magnetic fluid has been filled in advance between themagnetic force generating means and the sleeves, the fitting becomeseasy, and scattering of the magnetic fluid outside of the groove isprevented, so that management of the magnetic fluid filling amountbecomes easy. Also, it is possible to make the magnetic fluid slide inthe groove of the sleeve corresponding to the reciprocal movement lengthof the two members.

The oil-repellant film is formed on the opposing surface of the sleeveopposing the magnetic force generating means, whereby it is possible toprevent the magnetic fluid sliding at the time of relative reciprocalmovement from spreading on the surface and to prevent the magnetic fluidamount used in the seal from being reduced.

The sleeves have an elastic deformation characteristic that enables themagnetic force generating means to be inserted into the grooves of thesleeves, whereby smooth fitting of the magnetic force generating meansis possible.

The two members and the sleeves are nonmagnetic materials, whereby themagnetic fluid can be gathered at the magnetic poles of the magneticforce generating means and the magnetic force generating means can bemade to float magnetically.

The groove is formed in the opposing surface of at least one member ofthe two members opposing the magnetic force generating means, wherebymembers such as sleeves and pole pieces that have been usedconventionally become unnecessary, the device can be configured by onlythe magnetic force generating means and the magnetic fluid, structuralmembers can be reduced, and thinning becomes largely possible.

The oil-repellant film is formed on the opposing surface of at least onemember of the two members opposing the magnetic force generating means,whereby it is possible to prevent the magnetic fluid from spreading onthe surface of the one member and to prevent the magnetic fluid amountused in the seal from being reduced.

The magnetic force generating means has an elastic deformationcharacteristic that enables the magnetic force generating means to beinserted into the grooves, whereby smooth fitting of the magnetic forcegenerating means is possible.

The oil-repellant film is formed on the portion of the magnetic forcegenerating means that does not contact the magnetic fluid, whereby it ispossible to prevent the magnetic fluid from spreading on the surface ofthe magnetic force generating means and to prevent the magnetic fluidamount used in the seal from being reduced.

The cutout portion is formed in the portion of the magnetic forcegenerating means that does not contact the magnetic fluid, wherebyweight reduction of the magnetic force generating means is improved, andit is possible to make the magnetic force generating means float morereliably.

The cutout portion is formed in the side surface of the magnetic forcegenerating means extending between the two members, whereby weightreduction of the magnetic force generating means is improved, and itpossible to make the magnetic force generating means float morereliably.

The cutout portions are formed in center portions of opposing endsurfaces of the magnetic force generating means opposing the twomembers, whereby weight reduction of the magnetic force generating meansis improved, and it is possible to make the magnetic force generatingmeans float more reliably.

The magnetic force generating means is a magnet that is unipolarly ormultipolarly magnetized in the axial direction or the radial direction,whereby the magnet and the magnetic fluid fill the space between the twomembers and can seal the two members.

Also, in the invention, the nonmagnetic member is buoyantly supported bythe magnetic fluid, and the space between the two members is sealed bythe nonmagnetic member and the magnetic fluid, whereby the sum of thetwo gaps between each member surface of the two members and thenonmagnetic member becomes a tolerance of eccentricity of the twomembers, and the invention can exhibit sealability even if the precisionof the coaxiality is low. Also, members such as the pole pieces thathave been conventionally used become unnecessary, structural members canbe reduced, which is effective for thinning of the device, andmanufacturing becomes easy without the need to join members. Moreover,because the nonmagnetic member floats with a magnetic force by themagnetic fluid, the invention also exhibits a function as a rotationinertia damper using the nonmagnetic member as an inertial body andusing the magnetic fluid as viscous damping means. In particular,because the nonmagnetic member can be made thin and light withoutchanging the magnetic force, the nonmagnetic member can be made to floatmagnetically even if the diameter of the device is increased.

The groove is formed in the opposing surface of at least one of thesleeve-like magnetic force generating means opposing the nonmagneticmember, whereby the device can be fitted in a state in which themagnetic fluid has been filled in advance between the sleeve-likemagnetic force generating means and the nonmagnetic member, the fittingbecomes easy, and management of the magnetic fluid filling amountbecomes easy.

The sleeve-like magnetic force generating means include twocross-sectionally L-shaped members comprising the axial-directionportion and the projecting portion that projects in the radial directionfrom the axial-direction portion at the opposite end portion at theaxial direction, and the sleeve-like magnetic force generating means areconfigured by superposing the axial-direction portions of thecross-sectionally L-shaped members, whereby it becomes easy to disposethe nonmagnetic member in the grooves of the sleeve-like magnetic forcegenerating means. Also, because the invention can be configured withoutstructural parts having elastic deformability, the degree of freedomwith which materials can be selected is increased.

The oil-repellant film is formed on at least the surface portion,outside the groove, of the opposing surface of the sleeve-like magneticforce generating means opposing the nonmagnetic member, whereby it ispossible to prevent the magnetic fluid from spreading on the surfaceoutside the groove and to prevent the magnetic fluid amount used in theseal from being reduced.

The oil-repellant film is formed on at least both axial-direction endportions of the sleeve-like magnetic force generating means, whereby thedevice can be fitted in a state in which the magnetic fluid has beenfilled in advance between the sleeve-like magnetic force generatingmeans and the nonmagnetic member, the fitting becomes easy, andmanagement of the magnetic fluid filling amount becomes easy. Also, itis possible to prevent the magnetic fluid from spreading on bothaxial-direction end portions of the sleeve-like magnetic forcegenerating means and to prevent the magnetic fluid amount used in theseal from being reduced.

The two members are relatively reciprocally movable, and the sleeve-likemagnetic force generating means fitted together with at least one memberof the two members is extended in the axial direction corresponding tothe reciprocal movement length of the two members, whereby the devicecan be fitted in a state in which the magnetic fluid has been filled inadvance between the sleeve-like magnetic force generating means and thenonmagnetic member, the fitting becomes easy, and management of themagnetic fluid filling amount becomes easy. Also, the magnetic fluid canbe retained on the sleeve-like magnetic force generating means extendingin the axial direction corresponding to the reciprocal movement lengthof the two members.

The groove corresponding to the reciprocal movement length of the twomembers is formed in the opposing surface of the sleeve-like magneticforce generating means opposing the nonmagnetic member, whereby thedevice can be fitted in a state in which the magnetic fluid has beenfilled in advance between the sleeve-like magnetic force generatingmeans and the nonmagnetic member, the fitting becomes easy, andscattering of the magnetic fluid outside of the groove is prevented, sothat management of the magnetic fluid filling amount becomes easy. Also,the magnetic fluid can be retained in the groove of the sleeve-likemagnetic force generating means corresponding to the reciprocal movementlength of the two members.

The sleeve-like magnetic force generating means have an elasticdeformation characteristic that enables the nonmagnetic member to beinserted into the grooves of the sleeve-like magnetic force generatingmeans, whereby smooth fitting of the nonmagnetic member is possible.

The nonmagnetic member has an elastic deformation characteristic thatenables the nonmagnetic member to be inserted into the grooves of thesleeve-like magnetic force generating means, whereby smooth fitting ofthe nonmagnetic member is possible.

The oil-repellant film is formed on the portion of the nonmagneticmember that does not contact the magnetic fluid, whereby it is possibleto prevent the magnetic fluid from spreading on the surface of thenonmagnetic member and to prevent the magnetic fluid amount used in theseal from being reduced.

The cutout portion is formed in the portion of the nonmagnetic memberthat does not contact the magnetic fluid, whereby weight reduction ofthe nonmagnetic member is improved and it is possible to make thenonmagnetic member float more reliably.

The cutout portion is formed in the side surface of the nonmagneticmember extending between the two members, whereby weight reduction ofthe nonmagnetic member is improved and it is possible to make thenonmagnetic member float more reliably.

The cutout portions are formed in center portions of opposing endsurfaces of the nonmagnetic member opposing the two members, wherebyweight reduction of the nonmagnetic member is improved and it ispossible to make the nonmagnetic member float more reliably.

The sleeve-like magnetic force generating means is a magnet that isunipolarly or multipolarly magnetized in the axial direction or theradial direction, whereby the magnet is fitted to the two members andthe magnetic fluid can be retained.

1. A magnetic fluid seal device that seals a space between two membersthat are assembled so as to be mutually relatively movable, the magneticfluid seal device comprising: magnetic force generating means that isdisposed between the two members and generates a magnetic force; amagnetic fluid that is magnetically retained at opposing ends of themagnetic force generating means opposing the two members and that sealstwo gaps between the magnetic force generating means and each membersurface of the two members; and sleeves that are fitted together with atleast one member of the two members, a groove formed in opposingsurfaces of the sleeves oposing the magnetic force generating means, andthe magnetic force generating means being buoyantly supported by themagnetic fluid, and the space between the two members being sealed bythe magnetic force generating means and the magnetic fluid.
 2. Themagnetic fluid seal device as in claim 1, wherein the sleeves includetwo cross-sectionally L-shaped members comprising an axial-directionportion and a projecting portion that projects in a radial directionfrom the axial-direction portion at an opposite end portion at the axialdirection, the sleeves being configured by superposing theaxial-direction portions of the cross-sectionally L-shaped members. 3.The magnetic fluid seal device as in claim 1, wherein an oil-repellantfilm is formed on at least a surface portion, outside the groove, of theopposing surfaces of the sleeves opposing the magnetic force generatingmeans.
 4. The magnetic fluid seal device as in claim 1, wherein aportion of the sleeves that projects in a radial direction is configuredby a rubber-like elastic body.
 5. The magnetic fluid seal device as inclaim 1, wherein a portion of the sleeves that fits together with theone of the members is configured by a rubber-like elastic body.
 6. Themagnetic fluid seal device as in claim 1, wherein the opposing ends ofthe magnetic force generating means opposing the two members arepointed, and magnetic flux is concentrated at and the magnetic fluid ismagnetically retained at pointed tips thereof.
 7. The magnetic fluidseal device as in claim 6, wherein the grooves of the sleeves are formedin a shape that matches the pointed opposing ends of the magnetic forcegenerating means.
 8. The magnetic fluid seal device as in claim 7,wherein the gaps between the pointed opposing ends of the magnetic forcegenerating means and the grooves of the sleeves narrow towards the tipsof the pointed opposing ends of the magnetic force generating means. 9.The magnetic fluid seal device as in claim 6, wherein the pointedopposing ends of the magnetic force generating means arecross-sectionally triangular protruding shapes.
 10. The magnetic fluidseal device as in claim 6, wherein the pointed opposing ends of themagnetic force generating means are cross-sectionally arced protrudingshapes.
 11. The magnetic fluid seal device as in claim 1, wherein anoil-repellant film is formed on at least both axial-direction endportions of the sleeves.
 12. The magnetic fluid seal device as in claim1, wherein the two members are relatively reciprocally movable, andwherein the sleeves fit together with at least one of the two membersand extends in an axial direction corresponding to a reciprocal movementlength of the two members.
 13. The magnetic fluid seal device as inclaim 12, wherein a groove corresponding to the reciprocal movementlength of the two members is formed in an opposing surface of the sleeveopposing the magnetic force generating means.
 14. The magnetic fluidseal device as in claim 12, wherein an oil-repellant film is formed onthe opposing surface of the sleeve opposing the magnetic forcegenerating means.
 15. The magnetic fluid seal device as in claim 1,wherein at least one of the sleeves and the magnetic fluid seal devicehave an elastic deformation characteristic that enables the magneticforce generating means to be inserted into the grooves of the sleeves.16. The magnetic fluid seal device as in claim 1, wherein the twomembers and the sleeves are nonmagnetic materials.
 17. The magneticfluid seal device as in claim 1, wherein an oil-repellant film is formedon an opposing surface of at least one member of the two membersopposing the magnetic force generating means.
 18. The magnetic fluidseal device as in any one of claim 1, wherein an oil-repellant film isformed on a portion of the magnetic force generating means that does notcontact the magnetic fluid.
 19. The magnetic fluid seal device as inclaim 1, wherein a cutout portion is formed in a portion of the magneticforce generating means that does not contact the magnetic fluid.
 20. Themagnetic fluid seal device as in claim 19, wherein a cutout portion isformed in a side surface of the magnetic force generating meansextending between the two members.
 21. The magnetic fluid seal device asin claim 19, wherein cutout portions are formed in center portions ofopposing end surfaces of the magnetic force generating means opposingthe two members.
 22. The magnetic fluid seal device as in claim 1,wherein the magnetic force generating means is a magnet that isunipolarly or multipolarly magnetized in the axial direction or theradial direction.
 23. A magnetic fluid seal device that seals a spacebetween two members that are assembled so as to be mutually relativelymovable, the magnetic fluid seal device characterized by including:sleeve-like magnetic force generating means that are respectively fittedtogether with the two members and generate a magnetic force; anonmagnetic member that is disposed between the sleeve-like magneticforce generating means; and magnetic fluid that is magnetically retainedat opposing surfaces of the sleeve-like magnetic force generating meansopposing the nonmagnetic member and that seals two gaps between thesleeve-like magnetic force generating means and the nonmagnetic member,wherein the nonmagnetic member is buoyantly supported by the magneticfluid, and the space between the two members is sealed by thenonmagnetic member and the magnetic fluid.
 24. The magnetic fluid sealdevice as in claim 23, wherein a groove is formed in an opposing surfaceof at least one of the sleeve-like magnetic force generating meansopposing the nonmagnetic member.
 25. The magnetic fluid seal device asin claim 24, wherein the sleeve-like magnetic force generating meansinclude two cross-sectionally L-shaped members comprising anaxial-direction portion and a projecting portion that projects in aradial direction from the axial-direction portion at an opposite endportion at the axial direction, the sleeve-like magnetic forcegenerating means being configured by superposing the axial-directionportions of the cross-sectionally L-shaped members.
 26. The magneticfluid seal device as in claim 24, wherein an oil-repellant film isformed on at least a surface portion, outside the groove, of theopposing surface of the sleeve-like magnetic force generating meansopposing the nonmagnetic member.
 27. The magnetic fluid seal device asin claim 24, wherein the sleeve-like magnetic force generating meanshave an elastic deformation characteristic that enables the nonmagneticmember to be inserted into the grooves of the sleeve-like magnetic forcegenerating means.
 28. The magnetic fluid seal device as in claim 24,wherein the nonmagnetic member has an elastic deformation characteristicthat enables the nonmagnetic member to be inserted into the grooves ofthe sleeve-like magnetic force generating means.
 29. The magnetic fluidseal device as in claim 23, wherein an oil-repellant film is formed onat least both axial-direction end portions of the sleeve-like magneticforce generating means.
 30. The magnetic fluid seal device as in claim23, wherein the two members are relatively reciprocally movable, and thesleeve-like magnetic force generating means fitted together with atleast one member of the two members is extended in an axial directioncorresponding to a reciprocal movement length of the two members. 31.The magnetic fluid seal device as in claim 30, wherein a groovecorresponding to the reciprocal movement length of the two members isformed in an opposing surface of the sleeve-like magnetic forcegenerating means opposing the nonmagnetic member.
 32. The magnetic fluidseal device as in claim 23, wherein an oil-repellant film is formed on aportion of the nonmagnetic member that does not contact the magneticfluid.
 33. The magnetic fluid seal device as in claims 23, wherein acutout portion is formed in a portion of the nonmagnetic member thatdoes not contact the magnetic fluid.
 34. The magnetic fluid seal deviceas in claim 33, wherein a cutout portion is formed in a side surface ofthe nonmagnetic member extending between the two members.
 35. Themagnetic fluid seal device as in claim 33, wherein cutout portions areformed in center portions of opposing end surfaces of the nonmagneticmember opposing the two members.
 36. The magnetic fluid seal device asin claim 23, wherein the sleeve-like magnetic force generating means isa magnet that is unipolarly or multipolarly magnetized in the axialdirection or the radial direction.